1996 Oldsmobile Ciera - Red Brake Light On

[Slacker]

Hi All,

The red brake light on dashboard is staying on even after the car is started. I know usually that's due to low fluid or the e-brake being on but neither of those are the case.

After the brake light went on I changed (they needed to be changed anyway, just so happened light turned on before I had a chance to do it.)

• Rear brake hardware
• Rear brake shoes
• Rear brake drums
• Front calipers
• Front caliper hoses
• Front brake pads

I also bled the brakes after doing the above work.

The light is still on though. Any ideas where to look? I'm guessing it's probably either a fluid level sensor or e-brake switch?

Thanks in advance!

[tlc1976]

Double check the e brake. I?ve bumped it before just enough to set off the light just by getting in the car. Make sure it retracts fully after your brake work too. It could also be the fluid level sensor or a bad wire or connection.

Don?t know if a 96 has the light controlled through the computer. But if not, then a little trick I?ve noticed is the light will get just a little bit brighter when both faults are happening. You can use this to your advantage. Say the real problem is something with the fluid. So if you push the e brake, the light will get a little bit brighter. But if the problem is e brake related, pushing the e brake won?t change the brightness.

[Pontiac6ksteawd]

The fluid level sensor may have gone bad to. If I remember correctly, its a simple plug on the side of the reservoir, unplug it, check if the light is on or off (engine running), if its on, take a paperclip, and jump the terminals in the plug, check for light again.. If the light goes out in either case, its just a bad brake fluid level sensor. They dont normally fail, but anything electrical can fail.

[Slacker]

Sorry for the late update on this.

I tried popping and setting the ebrake a bunch thinking maybe something was stuck. No change there.

I also tried unplugging the fluid sensor on the side of the reservoir. No change as well.

Finally, I tried using a paper clip to short the connector on the plug and nothing changed with the brake light.

I tried to notice if the light got brighter at all during any if this and it didn't.

This all started when I had to push the car with it off due to a dead battery. When I pushed hard on the brakes, the light came on. This was before I replaced everything...

Any other ideas on what to check? Fluid level is full as well.

[tlc1976]

Check the switch at the e brake? Try unplugging it, and try jumping the connector to see if anything changes.

Other than that, all I can think of is a short in the instrument cluster, but it should affect the other lights the same.

I?ve heard of the brake fluid switch detecting the position of a spool that will shift position if a line blows and the system goes off balance. But regardless, the light would have gone off when you bypass that switch.

Does the car have abs?

[Keiths1976]

How about this check all the third brake light bulbs and brake lights them selves . Sometimes u get corrosion on the bulbs sockets and will create a short and cause the light to come on . Being a 96 car she most likely has abs . U can pull the negative off the battery for a few minutes and then hook it back up see if that clears it out . Also since abs stores the codes of there is a brake related issue abs light comes on as well . Brake light switch wouldnt really kick the light on but the light bulbs to the third light and back rail light bulbs can . Have a 95 that did this crap and turned out to be a corroded bulb socket . Also the drivers rear inner wheel well in the trunk has the harness for the rear tail lights take a look and see if there is corrosion . Basically shorting that out

[Slacker]

Thanks for the suggestions.

I checked all the rear brake lights and all bulbs light up when the brake is pressed.

I checked the ebrake switch behind the ebrake pedal. Where the pedal is in the full up position does put the switch in the "clicked in" position. I clicked it on and off with my hand and didn't see the light change on the dash.

I tried unplugging the connector on the side but it was stuck on pretty good. When it did come loose, the whole connector popped out from inside the switch.. which I guess would be like unplugging it in a way. No change with the dash light.

The car does have abs but that's a different dash light.

[tlc1976]

I don?t have a 96 diagram. But on the older cars the light was controlled by analog switches. I wonder if maybe on the 96, the switches might just feed the ECM with the light controlled by the ECM.

[Slacker]

I don?t have a 96 diagram. But on the older cars the light was controlled by analog switches. I wonder if maybe on the 96, the switches might just feed the ECM with the light controlled by the ECM.

After today, I'm starting to wonder the same thing...

I took the ebrake switch out to inspect it and reassemble it after I managed to pull it apart the other day. Switch is in good condition. Fiddled around with it more to see if it would do anything with the light but it didn't. I tried grounding and lifting the ground as that seems to be how it works with the screw that attaches it to the car.


Tried again plugging/unplugging/shorting the connector for the level sensor. Sensor circled in red, connector is in my hand on the right. No luck.



The brake pedal itself has these three plugs associated with it. I tried pulling them off one by one to see if there was any change. There wasn't on the dash but after I pulled the last one off, the rear brake lights no longer worked until I plugged it back in.


Those look to be these:


Checked the wiring harness in the trunk as well as the connector. It all looks good. I think me unplugging it today was the first time it was ever unplugged. Car dies right away if you try to start it with the harness unplugged. I'm guessing one of the wires goes to the fuel pump or something?


...and just for the heck of it, here's the dash light.


One interesting thing that I noticed today was that the brake light is on at key-on-engine-off, turns off while cranking and then about 1/2 a second after the car starts, the light comes back on. When I short the level sensor connector that goes to the master cylinder, the light stays on without the brief pause of turning off. I figured I would mention it in case that helps.

Thanks for all the help so far!

Edit:
I wonder if maybe this might be why the issue didn't clear up with the brake parts getting replaced and lines bled? When I bled the brakes, I did the traditional farthest away from the master cylinder in the back and then went from there. (Passenger rear, driver rear, passenger front, driver front).

Prior to bleeding the rear brakes, the rear displacement cylinder must be returned to the top-most position. This can be accomplished using the Tech I scan tool or equivalent, by entering the manual control function and applying the rear motor. If a scan tool is unavailable, bleed the front brakes. Ensure the pedal is firm. Carefully drive the vehicle to a speed above 4 mph to cause the ABS system to initialize. This will return the rear displacement cylinder to the top-most position.

I wonder if I have an uneven pressure between the front and rear lines due to not following the instructions above that's maybe causing the light to go on? I would think bypassing the switch would cover that unless it's looking for a specific resistance or something when in the correct range.

All dual circuit system uses a switch to warn the driver when only half of the brake system is operational. This switch is located in a valve body which is mounted on the master cylinder. A hydraulic piston receives pressure from both circuits, each circuit's pressure being applied to one end of the piston. When the pressures are in balance, the piston remains stationary. When one circuit has a leak, however, the greater pressure in that circuit during application of the brakes will push the piston to one side, closing the switch and activating the brake warning light.

[Keiths1976]

The abs light could steer u in the right direction unless that?s key on only . Also the master cylinder /abs module attached are one unit . For giggles there is a fuse for the pusher fan in the fuse box labeled that has a power source to the abs pump and relay . I?m starting to thing you are throwing a code in the abs that is leading to your brake light . Even wheel speed sensors for the abs will throw both on . I?d find the pusher fan fuse top upper right on the 95 Buick century it?s there for yours . Pull it while the car is running then pop it back in the abs pump will click prime the check engine light abs light and brake light will go out . You just cleared the codes in the abs then see if it comes back on . Also when you bleed them did you ever run the master cylinder dry or below the brake light switch and it?s a hard code stored in the abs system .

[Keiths1976]

The system way back in the day shops use to gravity bleed them and be done others used the tech 1 scanner to prime and bleed them . Last option for the obd1 a-body cars was someone key on key off and they bleed the back brakes which cause the rear drum brakes to prime first . But all that took longer with the key on off method . But for giggles pop the rear drums off and make sure no wheel cylinders seals were popped or torn and the light is detected cause pressure is being loses soon first key on priming the abs system .

[Keiths1976]

The 96 a body cars have the same abs system at 93-5 . If the car stops firmly not pulls to the side upon 35 mph panic stops. The system is complete even pressure . The light then is electrical issues clean them out with the fuse I stated . Shoot me a email mx67627@aol.com

[Slacker]

No luck with the fuse. When I pull it while the car is running, the brake light and the headlights go off but the ABS light stays on. As soon as I plug the fuse back in, it turns the brake light back on.

I'm not able to test the panic stop because some jerk popped both tires on my one side one night while it was parked on the street and I need to order new ones. I don't remember it pulling after replacing the brake stuff earlier in the year though.

Hopefully, in the next week I can try and re-bleed the brakes again.

[Keiths1976]

U have a wheel speed sensor issue if that abs stays on 9-10 front wheel bearing /abs ring

[Slacker]

I found the dash schematic from this thread: https://www.a-body.net/forums/showth...clusters/page2


It looks like the only things on there besides the brake control module are the brake fluid level switch and the parking brake switch. So, I guess that would make sense if that control module can turn the light on. I'm guessing the lamp is getting its ground to turn on from that?

This is the part you're saying needs to be replaced, right? https://www.rockauto.com/en/catalog/...ing+&+hub,1636
Any idea how much of pain they are to swap out? It looks like it might just be bolt on instead of needing to be pressed? I figure I should do both sides in the front.